Please read the sticky at the top "Sound System Improvement, Stage One". I have given a good better best break down. And although some of the equipment has been updated (Alpine sps-400 are now sps-410) the idea is the same.

Short answer is no it is not a one for one replacement where you can swap out the H/U with an aftermarket and get audio right away.

Be prepared to spend $600-800 to replace H/U and speakers along with installer fees (depending on what they charge in your area).

Replacing the speakers are a breeze with some patience and minor tools. That is covered in the sticky.

I would start there.

I was going to do some trouble shooting pics for an earlier question, but I am a victim of the widespread power outage on the NE coast and it will have to wait.